Large scale agricultural planters typically employ a number of row crop planter units attached in a side-by-side, spaced manner to a support frame which is drawn by a tractor. Each of the row units has a seed meter employing either discs or plates rotating in a vertical plane for grasping and discharging the seeds at a given discharge rate. The discharge rate may be changed depending upon the type of crop, the soil condition and type, and the characteristics of the terrain. For example, in the corners of a field having a center circular irrigation system it is desirable to reduce the planting population rate in accordance with the reduced capability of the drier soil to support the crop. In this and similar situations, it is desirable to be able to easily and quickly change from one planting population rate to another while the implement traverses the field.
One prior art approach to changing the planting population rate involves changing sprocket and gear combinations attached to various shafts. This approach requires the implement to be stopped for as long as ten minutes while one or more chains or belts are moved and positioned about various sized sprockets or gears. This approach not only takes the implement out of operation for a considerable time, but also requires additional work by the operator. Some more recent approaches such as disclosed in U.S. Pat. No. 4,623,078 afford the capability to adjust the planting population rate while continuously planting. While the '078 patent discloses a two-speed planter drive unit, it does not afford complete disengagement of the planter unit from the drive unit which is frequently desirable under certain circumstances. For example, depending on the soil conditions including the moisture content, it may be desirable to continue planting with some of the planter units such as on one side of the tractor centerline, while discontinuing planting with those planter units to the other side of the tractor centerline. This capability is not available in the '078 patent and requires removing the implement from service which is costly, time consuming and inconvenient.
The present invention addresses the aforementioned limitations of the prior art by affording on-the-go control in a dual-speed clutch arrangement for selecting a higher or lower planting population rate in a planter implement having a plurality of spaced row units and further offers the advantage of quickly and easily disconnecting some or all of the individual row units from the input drive.